5.8.9.4.1. Implementation 
Depending on the COP parameter DTMP for the line, the system generates
a ground pulse (DTMF not set) or a loop interruption (DTMF set). It is
not possible to replicate an AnaTe with DTMF dialing and ground key.
When the ground pulse or the flash pulse ends, the trunk returns to
the talking state.
You can set the ground pulse or flash for BWMSCH lines with the AMP
PTIME, parameter TBLK for BWMSCH under L3 and L4. L3 contains the time
for the ground pulse (default: 240 ms) and L4 the time for the flash
(default: 120 ms).
IMPORTANT:
NOTE for BWMSCH lines The ground is applied only
to the ring wire in the ground pulse. You must check the wiring because
the tip and ring wires are no longer polarity-independent.